Guanfacine Starting Dose for ADHD
The recommended starting dose of guanfacine for ADHD treatment is 1 mg once daily, administered in the evening to minimize somnolence. 1, 2
Dosing Guidelines for Guanfacine in ADHD
- Guanfacine is available in extended-release tablet form with doses of 1,2,3, and 4 mg for ADHD treatment 1
- The general dosing principle is approximately 0.1 mg/kg administered once daily 1
- Evening dosing is often preferred due to the common side effect of somnolence 1
- Initial dose should be 1 mg daily, with potential titration after 3-4 weeks if the clinical response is inadequate 2
Titration and Dose Adjustment
- If the 1 mg dose does not provide satisfactory results after 3-4 weeks, the dose may be increased to 2 mg 2
- Most therapeutic effects of guanfacine are observed at the 1 mg dose 2
- Higher daily doses have been used, but adverse reactions increase significantly with doses above 3 mg/day 2
- Unlike stimulants, treatment effects are not usually observed until 2-4 weeks after initiation 1
Safety and Adverse Effects
- The most common treatment-emergent adverse events are somnolence-related (38.6%), headaches (20.5%), and fatigue (15.2%) 3
- Somnolence, sedation, and fatigue typically emerge within the first 2 weeks of dosing and generally resolve by the end of treatment 4
- Other adverse effects include irritability, insomnia, nightmares, and potential cardiovascular effects (hypotension/bradycardia) 1
- Approximately 80% of patients may experience at least one treatment-emergent adverse event 3
Special Considerations
- Guanfacine has higher specificity for alpha-2A receptors compared to clonidine, potentially resulting in fewer sedative effects 1
- In Europe, guanfacine is only approved when stimulants are not suitable, not tolerated, or ineffective 1
- Pharmacokinetic studies show that plasma concentrations and concentration-related parameters are higher in children than in adolescents, likely due to weight differences 5
- Guanfacine extended-release has demonstrated linear pharmacokinetics with a half-life of approximately 14-18 hours 5
Monitoring and Follow-up
- Blood pressure and heart rate should be monitored, as guanfacine can cause decreases in these parameters that are dose-dependent 4
- Mean heart rate and blood pressure typically decrease as the dose increases but return toward baseline during dose maintenance and tapering 4
- If discontinuing guanfacine, gradual tapering is generally recommended, although studies suggest that abrupt cessation may not cause significant rebound hypertension compared to tapering 6